Title of Invention

A PROCESS FOR THE PREPARATION OF A NEW CATALYST USEFUL FOR OXIDATION REACTIONS

Abstract

A process for the preparation of a new catalyst useful for oxidation reactions by co-precipitation of the mixed oxide support by known precipitation method and impregnating the active oxide on the mixed oxide support material as obtained above by conventional methods, drying the impregnated material at a temperature of 373-393 K, adding promoter oxides to the dried impregnated material, drying again and calcining the material at a temperature in the range of 773 K to 973 for 6 to 16 hours to obtain the catalyst.

Full Text

The present invention relates to a process for the preparation of a new catalyst useful for oxidation reactions. The present invention particularly relates to a process for the preparation of a highly active and selective oxidation catalyst. The catalyst prepared by the process of the present invention is useful for the preparation of substituted benzaldehydes in high yields. Among various substituted benzaldehydes, the p- •*?• tf methoxybenzaldehyde (p-anisaldehyde) is an important chemical and chemical intermediate having many potential applications. For %xample, ithe p-methoxybenzaldehyde is used as a perfumer, brightener in plating, and raw material for the preparation of Pharmaceuticals and agrochemicals. The substituted benzaldehydes are hitherto being prepared by a vapour phase reaction of a gases mixture consisting of substituted toluenes and air over a mixed oxide based promoted vanadium oxide catalyst. For the vapour phase catalytic oxidation of substituted toluenes to get the corresponding aldehydes only a limited number of processes are reported. A Japanese patent publication No: 85/100, 582 discloses a catalyst comprising of a mixture of vanadium oxide with some of the elements like sodium, potassium, and rubidium from lA-group, and also one of the elements from IIA-group like magnesium, calcium, etc., are used for the conversion of 4-methylanisole to anisaldehyde. This process however produces only limited yields of the benzaldehyde derivatives at 773 K operating temperature. Another Japanese patent publication No: 02 53, 750, discloses a catalyst consisting of the elements of vanadium and silver oxide, optionally containing some other oxides selected from potassium, copper, phosphorus, antimony, bismuth, tin, and lead at 593 K. In another method, Nippon Shokubai Kagaku Kogyo Company Limited, Japan (European patent No: EP 228, 275), reported a catalyst prepared by calcining the product of a dried mixture containing ammonium metavanadate, cesium nitrate, copper nitrate and cellite materials. Another patent assigned to Nippon Shokubai Kagaku Kogyo Company Limited, Japan (Japan patent application No: 84 /198, 698) a catalyst consisting of elements of vanadium, rubidium and/or Cs, and K and other elements selected from Cu, Ag, P, Sb, and Bi are used for the reaction of 4-methylanisole to anisaldehyde. Nevertheless, the catalysts mentioned above involve many problems left unsolved for industrial production point of view such as necessity of using large excess of air or nitrogen and oxygen mixture, catalyst deactivation, low yields of aldehydes, high reaction temperatures etc. The main objective of the present invention is to provide a process for the preparation of new catalyst useful for oxidation reactions which obviates the drawbacks of known catalyst. Another object of the present invention is to provide process for the preparation of highly active and selective catalyst useful for producing substituted benzaldehydes in greater yields by vapour phase selective oxidation, which overcomes the drawbacks of the hitherto known processes. In our copending application No.807/Del/99 we have claimed a process for the preparation of substituted benzaldehydes using the present catalyst. In view of the above, the present invention as a result of extensive research could overcome such disadvantages to bring out a catalyst comprising oxides of vanadium, molybdenum, titanium and gallium prepared through a homogeneous co-precipitation method using urea as hydrolyzing method. This novel catalyst possesses acid and base characteristics together with redox properties. Combining these three important properties together in desired proportion in a single catalyst is an important achievement in the area of catalyst making,. Combining acid-base characteristics together with redox properties in a desired proportion on a single catalyst is the significant notability of this new catalyst. The above said three important charactertistics are highly essential for any catalyst that is to be active and selective for selective oxidation reactions. The objective of the present invention was to provide a process for the preparation of a catalyst by making titanium and gallium oxides together by a homogeneous co-precipitation method and impregnating vanadium oxide and/or molybdenum oxide over the support material. Accordingly, the present invention provides a process for the preparation of a new catalyst useful for oxidation reactions which comprises the coprecipitation of the mixed oxide support by known precipitation method and impregnating the active oxide on the mixed oxide support material as obtained above by conventional methods, drying the impregnated material at a temperature of 373-393 K, adding promoter oxides to the dried impregnated material, drying again and calcining the material at a temperature in the range of 773 K to 973 for 6 to 16 hours to obtain the catalyst. In an embodiment of the present invention the support material used may be such as titania-gallia, titania-silica, titania-alumina, titania-zirconia, calcium-magnesium and titania-lanthanum and mixtures thereof. In another embodiment of the present invention the active compound used may be in the range of 5-20 wt %.. In yet another embodiment of the invention the composition of mixed oxide varies in the range of 1 to 5 mole %. In still another embodiment the calcination temperature of the mixed oxide support and the impregnated catalyst may range from 673 to 973 K for 6 to 16 hr. In further embodiment of the invention the promoter oxide used may be such as potassium, cobalt, cesium, silver and manganese. In yet another embodiment the active oxide component used may be such as vanadium, molybdenum, and tungsten. EXAMPLE 1 The titanium-gallium oxide (5 : 1 mole ratio) in particular is prepared by a homogeneous co-precipitation method. The cold titanium chloride (48.5 g) was first digested in cold concentrated hydrochloric acid (200 g) and subsequently diluted with distilled water (300 g). To this, the gallium oxide (9.6 g) dissolved separately in concentrated HC1 (150 g) was added. To the obtained mixture solution an excess amount of solid urea (800 g) was added and heated to 368 K with vigorous stirring. In about 6 hours of heating, as decomposition of urea progressed to a certain extent, the formation of precipitate gradually occurred and the pH value of the solution increased. The precipitate was further heated to facilitate aging. The coprecipitate obtained was flittered off and washed thoroughly with doubly distilled water until no chloride ions could be detected with Ag+ in the filtrate. The obtained cake was then oven dried at 393 K for 16 hours and calcined at 773 K for 6 hours in open-air atmosphere. In distilled water (200 g) kept at 363 K ammonium metavanadate (5.3 g) was dissolved with stirring and to this solution a 2 mole % oxalic acid (40 g) was added and reacted for 2 hours to obtain a clear ammonium metavanadate solution. To this solution the above mixed oxide support (30 g) was added and the reaction mixture solution was concentrated and dried at 383 K for 16 hours followed by calcination at 773 K for 8 hours in air. The catalyst (5 g) was filled in the Pyrex glass reactor of 10 mm I.D. and 500 mm long. The catalyst was preconditioned in a flow of dry air at 723 K for a period of 4 hours. Air (50 ml/min) or a mixture of nitrogen and oxygen were supplied to the reactor through cylinders. The liquid reactant was fed at a rate of 2.5 ml per hour to the reactor through pre-calibrated liquid syringe pump. With heating the catalyst portion of the reactor at 773 k, a gaseous mixture of 4-methyl toluene and air was flowed through the reactor and the reacted gaseous mixture was trapped by cold traps and analyzed by gas chromatography. The overall conversion of 4-methylanisole was between 76 - 96% and the anisaldehyde yield was between 65 - 85%. EXAMPLE 2 The reaction was carried out in the same manner as in example 1, but the catalyst used was Mo promoter oxide impregnated one. Ammonium heptamolybdate (5 wt %), was dissolved in water and impregnated to the oven dried catalyst sample. To make the oven dried catalyst sample, in distilled water (200 g) kept at 363 K ammonium metavanadate (5.3 g) was dissolved with stirring and to the solution a 2 mole % oxalic acid (40 g) was added and reacted for 2 hours to obtain a clear ammonium metavanadate solution. To this solution the mixed oxide support (30 g) was added and the reaction mixture solution was concentrated and dried at 383 K for 16 hours. The obtained catalyst sample was oven dried again and calcined at 773 K for 6 hours. The percentage conversion of 4-methylanisole and the corresponding aldehyde yields were in the range of 80 - 96 % and 70 - 86 % respectively. EXAMPLES The catalyst used was calcium-magnesium oxide (1:1 mole ratio) supported one. The support material was prepared by hydrolysis of calcium chloride and magnesium chloride together. To achieve this a known quantity of calcium chloride (73 g) and magnesium chloride (48 g) were dissolved in distilled water (400 g) and to which an excess amount of urea (600 g) was added and heated to 363 K for 24 hours. The obtained precipitates were washed thoroughly with deionized water until free from chloride impurities and dried in oven for 24 hours at 393 K and calcined at 973 K for 8 hours. Vanadium oxide from ammonium metavanadated was impregnated on the support material and was subsequently dried at 393 K for 12 hours and finally calcined at 773 K for 6 hours. The average conversion of 4-methylanisole was 75 - 90 % and the aldehyde product selectivity was 70 - 80 %. EXAMPLE 4 The gallium-titanium (1:5 mole ratio) mixed oxide support was prepared by a homogeneous precipitation method. The cold titanium chloride (48.5 g) was first digested in cold concentrated hydrochloric acid (200 g) and subsequently diluted with distilled water (300 g). To this, the gallium oxide (9.6 g) dissolved separately in concentrated HC1 (150 g) was added. To the obtained mixture solution an excess amount of solid urea (800 g) was added and heated to 368 K with vigorous stirring. The co-precipitate thus obtained was filtered off and washed thoroughly with doubly distilled water until no chloride ions could be detected with Ag+ in the filtrate. The obtained cake was then oven dried at 393 K for 16 hours and calcined at 773 K for 6 hours in open-air atmosphere. To this support the vanadium and molybdenum oxide active components were co-impregnated on the TiO2-Ga2O3 mixed oxide support. The requisite quantities of ammonium metavanadate (2.65 g) and ammonium heptamolybdate (2.65 g) were dissolved separately and mixed together, to which the support oxide (20 g) was added. The impregnated sample was oven died at 393 K and calcined in the range of 773 K. The catalyst sample was further preactivated with dry air and oxygen for 6 hours. On average, the conversion amounted to 82 - 96% and the product yield to 68 - 86%. We claim : 1. A process for the preparation of a new catalyst useful for oxidation reactions which comprises the coprecipitation of the mixed oxide support by known precipitation method and impregnating the active oxide on the mixed oxide support material as obtained above by conventional methods, drying the impregnated material at a temperature of 373-393 K, adding promoter oxides to the dried impregnated material, drying again and calcining the material at a temperature in the range of 773 K to 973 for 6 to 16 hours to obtain the catalyst. 2. A process as claimed in claim 1 wherein the mixed oxide support material is selected from titania-gallia, titania-silica, titania-alumina, titania-zirconia, calcium- magnesium and titania-lanthanum and mixtures thereof. 3. A process as claimed in claims 1-2 wherein the active oxide selected from vanadium, molybdenum & tungsten and the amount of active oxide component used ranges from 5 to 20 wt%. 4. A process as claimed in claims 1-3 wherein the composition of mixed oxide varies in the range of 1 to 5 mole%. 5. A process as claimed in claims 1-4 wherein the promoter oxide is selected from potassium, cobalt, cesium, silver and manganese. 6. A process for the preparation of a new catalyst useful for oxidation reactions substantially as herein described with reference to the examples.

Documents:

809-del-1999-abstract.pdf

809-del-1999-claims.pdf

809-del-1999-correspondence-others.pdf

809-del-1999-correspondence-po.pdf

809-del-1999-description (complete).pdf

809-del-1999-form-1.pdf

809-del-1999-form-19.pdf

809-del-1999-form-2.pdf